On Thu, Feb 19, 2015 at 8:45 PM, Juliusz Chroboczek <[email protected]> wrote: >> A marginal link is simply one that has a measurable amount of packet loss. > > Ok, re-reading this exchange, it looks like I may have wrongly assumed > that people are aware of background. I'll need to put that into the > routing comparison document, this is as good a place as any to draft my > text. > > Carrier and enterprise routing protocols are optimised for wired networks, > where a link is either down (drops all packets) or up (drops one packet in > 10^10). > > Home networks usually include link technologies that have an intermediate > "marginal" state: a link that drops a non-negligible fraction of packets. > With 802.11, in particular, marginal links have fairly unpleasant performance > characteristics. For example, if the BER is 10^-4, > > - multicast packets are dropped at roughly the nominal rate (10% for 120 > byte packets, 90% for 1500 byte packets); > - unicast packets are dropped at a much lower rate, but the efficiency > suffers (0.9 for 120 byte packets, 0.1 for 1500 byte packets). > - unicast packets have a high probability of being duplicated (no > figures given, I'm too lazy to look up the size of an ACK frame). > > This is of course a very naive analysis -- in practice, errors tend to > come in bursts, and furthermore 802.11a/g/n implements some very complex > lower-layer magic. Don't believe any results from computation or > simulation, with radio, only actual testing in real-world networks is > trustworthy.
There is also the really bad case of wifi links without packet loss which are stable at 6 Mbit/s... stable but incredible slow. If you have a combination of two 450 Mbit/s links you can use instead, you want to do it... Henning Rogge _______________________________________________ homenet mailing list [email protected] https://www.ietf.org/mailman/listinfo/homenet
